Excited states and reduced transition probabilities in Os 168

The level scheme of the neutron-deficient nuclide168Os has been extended and mean lifetimes of excited states have been measured by the recoildistance Doppler-shift method using the JUROGAM \ gamma-ray spectrometerin conjunction with the IKP K\"oln plungerdevice. The 168Os \gamma rays were measured in delayed coincidence with recoilingfusion-evaporation residues detected at the focal plane of the RITU gas-filled separator. The ratio of reduced transition probabilities B(E2;4_1^+ \rightarrow 2_1^+)/B(E2;2_1^+ \rightarrow 0_1^+) is measured to be 0.34(18), which is very unusual for collective band structures and cannot be reproduced by IBM-2 model calculations based on the SkM* energy-density functional.